This invention generally relates to cardiac mapping, more particularly to surface mapping electrode sets and the making of same, which surface mapping electrode sets are suitable for conducting epicardial and/or endocardial mapping. Electrode sets according to this invention include an administration portion or head, a plurality of insulated wires that are positioned generally longitudinally adjacent to each other and that each have a distal end embedded within the head portion which has an administration surface. Making the electrode set includes slitting the insulation of the administration surface at locations above the electrodes, and each portion of each electrode that is exposed by each slit is pulled or bent outwardly to form a generally arcuate electrode that projects through the slit. The plurality of thus formed generally arcuate electrodes form a set of electrodes that are suitable for mapping of cardiac surfaces.
Mapping electrode sets for epicardial and endocardial mapping of heart signals have been provided in the past. Typically, these mapping electrode sets are utilized during cardiac surgery in order to sense the cardiac signal and report it to the surgical team through appropriate display and/or printout devices. The surgical team may observe the reported data and immediately utilize the data in connection with a surgical procedure, or the data may be collected for subsequent analysis. Such mapping involves timing that is based upon the leading edge of an excitation wave through conductive tissue of the heart. Generally, mapping procedures include the induction of tachycardia while the mapping electrode is positioned on the cardiac tissue by the surgeon.
Various structures of mapping electrode sets have been developed or proposed. Many of these structures require somewhat complicated and difficult fabrication techniques. Also, these mapping electrode sets typically include electrodes that are the distal tips of the wires which transmit the signals to the data receiving unit, which distal tips project beyond the administration surface of the mapping device. Often, these projecting distal tips of the electrode wires must be modified in some manner in order to provide a suitable electrode. For example, the distal tips may have a very small diameter or have somewhat sharp edges, both of which increase the possibility of penetration thereby of heart tissue or of trauma to the heart.
Techniques are available for modifying such wire tips in order to minimize the possibility of heart penetration or trauma. Included are means for modifying the configuration of the wire tip. Often, because the wires used in mapping devices are exceptionally thin, efforts to minimize heart tissue penetration and trauma most advantageously include increasing the size of the tip, such as by adding a blunt or spherical member thereto or by reshaping the tip. One type of acceptable procedure is to subject the wire tip to inert gas shielded arc welding, particularly inert gas welding that utilizes a non-consumable tungsten electrode, this procedure being known as TIG.
Another important consideration regarding mapping electrode sets is that they are disposable. Accordingly, economic factors strongly favor the use of components and procedures that minimize or decrease the cost of the mapping electrode set. It is also important that the mapping electrode set provide the surgeon with the ability to accurately position the electrodes at a desired location on the outside or inside surface of the heart so that the surgeon can very accurately determine the precise location of the blocked area of the tissue to be surgically removed or treated. Surface mapping electrode sets should therefore be easily maneuverable by the fingers of the surgeon.